1. Field of the Invention
The present invention relates to an apparatus for detecting and restoring physical identification (PID) data in an optical recording/reproducing system, and more particularly, to an apparatus for detecting and restoring PID data which is physical position information of sectors arranged on an optical disk surface.
2. Description of the Related Art
Recently, the spread of optical disk reproducing systems has rapidly risen. In particular, the capacity for storing data has become enormous due to the development of a new optical recording medium and a data compression method. Systems for searching for and reproducing an enormous amount of data at a high speed have been researched. Also, systems have been produced for recording predetermined data on an optical disk surface, as well as reproducing recorded data. Systems such as digital versatile disc read only memories (DVD-ROMs), DVD-RAMs, or compact disk rewritable (CD-RW) drives are good examples of optical disk recording/reproducing systems which presently are receiving much attention.
In the optical disk recording/reproducing systems as described above, the recording and reproducing of data must be preceded by the identification of the positions of the sectors arranged on the surface of the optical disk. On an optical disk, a header field has physical identification data (PID) to define the positions of the sectors arranged on the optical disk surface. The system detects and restores the PID data and identifies the location of a sector where a pickup is positioned. FIGS. 1A, 1B, 1C and 1D show the format of one sector among the plurality of sectors spirally arranged on a DVD-RAM disk.
The fact that a conventional optical disk recording/reproducing system can fail in detecting PID data will now be described with reference to FIGS. 1A, 1B, 1C and 1D. Referring to FIG. 1A, each of the sectors spirally arranged on a DVD-RAM disk has a 128-byte header field and a 2418-byte data field where user data is actually recorded. Referring to FIG. 1B, the header field includes four individual header fields each having a voltage frequency oscillator (VFO) field, an address mark (AM) field, a PID field, an identification error detection (IED) field, and a postAmble (PA) field. The VFO field is used to lock PLL synchronization of lead channel bits. The AM field of 3 bytes is used to provide synchronization timing for detecting the PID data located behind the AM field. The IED field is used as parity information for detecting a PID error, and the PA field is used as a gap for providing a time margin upon decoding PID data.
Referring to FIG. 1C, the PID field is roughly divided into a sector information field and a field where a sector number is recorded. Referring to FIG. 1D, the sector information field is sub-divided into a reserved field which is a signal-free section, a PID number field, a sector type field, and a layer number field. Data recorded in the PID number field is in the form of xe2x80x9cxe2x88x9201bxe2x80x9d, xe2x80x9cxe2x88x9210bxe2x80x9d or xe2x80x9c11bxe2x80x9d, and is used as identification information ID1 through ID4 of the header field. Information data indicating whether data can be recorded in a corresponding sector, is recorded in the sector type field, and its form is classified into the following:
xe2x80x9cxe2x88x92000bxe2x80x9d: read-only sector,
xe2x80x9cxe2x88x92001bxcx9c010bxe2x80x9d: reserved,
xe2x80x9cxe2x88x92100bxe2x80x9d: rewritable first sector in a track,
xe2x80x9cxe2x88x92101bxe2x80x9d: rewritable last sector in a track,
xe2x80x9cxe2x88x92110bxe2x80x9d: rewritable before last sector in a track, and
xe2x80x9cxe2x88x92111bxe2x80x9d: rewritable other sector in a track.
When data recorded in the layer number field is in the form of xe2x80x9cxe2x88x920bxe2x80x9d, the field denotes a layer 0, and when data recorded in the layer number field is in the form of xe2x80x9cxe2x88x921bxe2x80x9d, the field denotes a reserved field.
The waveform of a lead signal, that is, a signal picked-up from the header field of a sector having the above-described format, is shown in FIGS. 2A and 2B.
FIGS. 2A and 2B are waveform views of a lead signal in the header field of a groove sector and in the header field of a land sector, respectively. In general, the pit depth of a header field is greater than or smaller than the pit depth of a data field.
If the DC level value of a lead signal picked-up from the data field is set to xe2x80x9cAxe2x80x9d, the DC level value of a lead signal picked-up from the header field is greater than or smaller than the level A as shown in FIGS. 2A and 2B. FIG. 2A shows a lead signal waveform when the pit depth of header fields 1 and 2 is smaller than that of a data field, and a lead signal waveform when the pit depth of the header fields 3 and 4 is greater than that of a data field in the groove sector. As shown in FIG. 2B, a lead signal waveform contrary to the lead signal picked-up from the groove sector is obtained in the land sector.
A typical radio frequency (RF) amplification unit included in an optical disk recording/reproducing system amplifies the level of a lead signal read from a pickup portion to a level that can be processed in the next step, shapes the waveform of the amplified signal, and outputs the resultant signal to a digital signal processor (DSP) which acts as a data decoder. If a lead signal as shown in FIGS. 2A and 2B is input to the RF amplification unit, a peak signal and a bottom signal, which are types of window signals, as shown in FIG. 4, are generated by the RF amplification unit. An AM and PID detection unit detects AM and PID in the enable section of the peak and bottom signals, so that a control unit for performing general control of a system can finally determine a sector where a pickup is currently positioned.
However, if an optical disk surface is degraded due to repetition of recording/reproduction, or if various scratches exist on the optical disk surface due to the carelessness of a user, the peak signal and bottom signal described above will not be normally generated. The peak signal and bottom signal can also be erroneously generated within the data field. Accordingly, there is a need for an optical disk recording/reproducing system that properly detects and determines or restores PID data even in a case in which no peak signal and/or bottom signal is generated. Also, there is a need for an apparatus which can detect PID data in a normal manner even when signals similar to the peak and bottom signals are generated in the data field.
An object of the present invention is to provide an apparatus which can properly detect and restore PID data, which is physical position information of a sector, regardless of whether the surface of an optical disk is degraded or damaged, in an optical disk recording/reproducing system.
Another object of the present invention is to provide an apparatus which can properly detect and restore PID data in a digital versatile disk-random access memory (DVD-RAM) system even if peak and bottom signals are detected in a lead signal picked up in a data field.
Accordingly, to achieve the above objectives, the present invention provides an apparatus for detecting and restoring physical identification (PID) in an optical disk recording/reproducing system having a radio frequency amplification unit, the apparatus comprising; an address mark (AM) and PID detector for outputting an address mark detection signal and a PID pattern upon detecting an AM pattern, and the PID pattern from an eight-to-fourteen modulation (EFM) data stream in the enable section of input signals; a PID error detecting unit for detecting the generation or non-generation of an error by decoding the received PID pattern, and outputting a PID error signal; a sector counting unit for counting the remaining size of a corresponding sector and outputting a counted value as a channel bit clock counting value; a PID window generator for receiving the channel bit clock counting value from the sector counting unit, generating a window signal for PID detection when the counting of a sector is concluded, and outputting the window signal to the AM and PID detector; and a PID continuous determining unit for determining the continuity or noncontinuity of PID by monitoring the input of the address mark detection signal, and outputting a PID position information value, corresponding to a finally received address mark detection signal, to the sector counting unit when the counted value of the error signal is greater than a predetermined threshold value.